Hey Travis, I feel your pain...first of all, was it a lot of money?
Also I highly doubt IRS would seize anything in a short amount of time...however he could be going bankrupt. Then you may get something down the road but it may not be worth it depending on what he owes you. Do you know anyone else that did work for him? Obviously you're not the only one he's beating...other vendors, landlord, employees etc
try to find out as much as you can on your own...attorneys will charge big money for info you can dig up yourself.
Best of luck...